Having separate domains for Server Fault and Super User from that of Stack Overflow's, yet keeping Meta as Stack Overflow's subdomain seems arbitrary and unintuitive as opposed to the very intuitive way the URLs of the questions on Stack Overflow match the titles of that webpage's question itself.

The advantages of having short 2-3 letter subdomains would mean fewer words to type to jump between boards.

Also, links to the sister sites will take less space on a page, leaving plenty of room to include additional links to as-yet-unthought-of subdomains. It'll fit better in a small box or on one line at the bottom/side/top of the page even if there are like 10-20 of these 2-3 letter subdomains.

Coming back to my question, are there logical, technical or just reasons of convenience that I am overlooking to have a whole domain as opposed to having just a subdomain at Stack Overflow itself?

The only thing I could think of was separate login profiles. That is until I found Meta asked for one too! Do we really need separate login profiles for what is essentially a sister site running the same software with the only difference being the audience or a subset thereof? Seems to be an unnecessary extra step for new users who are just looking to expand their horizons.

Any indications (blog or an already asked question) that Server Fault and Super User may someday redirect to x.stackoverflow just like uservoice now directs to meta.stackoverflow?

For one thing it indicates hierarchy in the URL without taking too much space. As in subdivision of audience catered to on Stackoverflow, where audience could be dev, svr, usr, what-have-you
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facepalmdJul 16 '09 at 19:25

Yeah, but that requires us to view them all as "subsets" of StackOverflow. Which they aren't. So it makes no sense.
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Shog9♦Jul 16 '09 at 19:30

Ah I could have been more clearer. I meant the links could be like: dev | svr | usr instead of: stackoverflow.com | serverfault.com | superuser.com This way if years from now there are many more sub-divisions and god-forbid further subdivisions of those subdivisions it'll fit more compactly on the page
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facepalmdJul 16 '09 at 19:29